Cathode ray magnetic focusing device



April 8, 1947.

CATHODE RAY MAGNETIC FOCUSING DEVICE P.- T. SPROUL Filed Mardh 31, 1944FIG.

7 Sheets-Sheet 1 mvew roe P. T. SPROUL ATTORNEY April 8, 1947. P. 'r.SPROUL I CATHODE RAY MAGNETIC FOCUSING DEVICE Filed March 31, 1944 vSheets-Sheet z F/GJ INVENTVOR R T. SPROUL Maui/L61 M ATTORNEY April 8,1947. P. T. SPROUL CATHODE RAY MAGNETIC FOCUSING DEVICE 7 Sheets-Sheet 3INl ENTOR I? 7'. SPROUL Filed March 31, 1944 A TTORNEY April 8, 1947.P.- T. SPROUL Q 2,418,487

CATHODE RAY MAGNETIC FOCUSING DEVICE Filed March 31, 1944 7 sheets -shet4 INVENTOR P. 7.' SPROUL MAM c1v 7M ATTORNEY April 8, 1947. P. 'r.SPROUL 2,418,487

CATHODE RAY MAGNETIC FOCUSING DEVICE Filed March 31, 1944 7 Sheets-Sheet5 FIG. 9A

INVENTOR WW 6. 1M

ATTORNEY 'P. 7". SPROUL April 8, 1947. P. T. SPROUL CATHODE RAY MAGNETICFOCUSING DEVICE '7 Sheets-Sheet 6 Filed larch 31, 1944 INVENTOR P. T.SPROUL April 8, 1947. v P. 'r. SPROUL 7 2,418,487

GATHODE RAY MAGNETIC FOCUSING DEVICE Filed March 51, 1944 7 Sheets-Sheet7 IN l/E/V TOR R r SPROUL ATTORNEY Patented Apr. 8, 1947 .-uN1rEo'STATES' PATENT orrics a Philip '1. Sproul, Chatham, N. J., assignor toBell I Telephone Laboratories, Incorporated, v New York, N. Y., acorporation of New York r ApplicationMai-ch 31, 1944, Serial No. 528,911

1 1 i a Thisinvention relates to magnetic devices and more particularlyto magnetic focusing devices- V employed in connectionwith cathode rayoscillograph devices. A 8 An object of the invention is toimprove the 20Claims. (cizso-ici) efliciency of operation of the manipulative controlsfor the movable elements of the device.

Another object of the'invention is to overcome circular displacement ofthe beam of the'cathode ray device during collimation of the beam alongthe axis of the device.

Another object of the-invention is to faciliitate transverse movement ofthe beam to compensate for manufacturing inaccuracies in the alignmentof the beam source with respect to the axis of the screen of the device.7

A furthenobject of the invention is to attain uniform movement of-theadjustable components ,of' the focusing device to insure positivecorrectional influence on the beam'of the cathode ray device. 1

Another object of the .invention is to fabricate the assembly of thefocusing device in such a manner that inertia is avoided and differencesin expansion and contraction are compensated so that high operatingefliciency is attained.

In accordance with'this invention these objects and other advantages areobtained in a compact magnetic focusing and centering device or unitembodying a permanent magnet core surrounded by a cylindricalshunt,which is adjustable with respect to the core to vary the strength of thetrolled by link members coupled to rotating cam shafts extending throughthe structure.

In both forms of the invention the shunt is efliciently controlled toeliminate wastemotion and to achieve a uniform variation of fieldstrength in order that the magnetic unit may be employed with a tubeover an operating range of large magnitude. Similarly, the centeringring in both forms is controlled uniformly through the transverselymovable plates to insure displacement of the ring in two directionsperpendicular to each other to eliminate curvilinear travel .of the beamin centering it with respect to the axis of the cathode ray tube. Thesearrangements reduce the time necessary for centering the beam andcontribute to the stable directive control of the beam on the axialcenter of the screen of the cathode ray device.

A feature of the embodiments of this invention relates to the uniformadjustment of the shunt member reciprocally with respect to the core toflux field for focusing the electron beam, a slidable auxiliary magneticring being mounted on one end of the core which is adjustably movable intransverse directions to accurately center the beam along the axis ofthe cathode ray tube.

In a specific embodiment of the invention a rotatable sleeve isassociated with the shunt, the sleeve being actuated by a gear shaft toreciprocally adjust the shunt with respect to the sleeve and"c0remagnet. The auxiliary centering ring is transversely shifted with"respect to the axis 1 of the focusing device by slidable platesencompassing the ring. These plates are actuated by cams to alter theaxis of the ring eccentrically with respect to the axis of the focusingmagnet structure.

In another form, the sliding plates engage pins on the centering ringand the plates are convary the strength of the flux field in the gap andthereby increase the operating range of the device between focusingvoltages-from 3,000 to 7,000 volts. This is accomplished by providingpins on the shunt which travel in angularly directed slots in therotatable sleeve surrounding it and the pins slide in guideways formedby upright members clamping the core magnet between the end pole pieces.The rotation of the shunt is thereby prevented 'so that frictionalforces do not affect the reciprocal movement of the shunt and thecontrol thereof is more easilyattained.

the positive displacement of the centering ring with respect to the axisof the magnet structure in which the sliding plates. are mounted betweenbearing plates having edge guide portions which engage the movableplates and insure uniform transverse travel of the centering ring, Inthe other form the slidable plates are accurately guided in theirtransverse travel by the same guide members controlling the travel ofthe pins 1' on the reciprocally movable shunt member.

These and other features of the invention will be set forth more indetail in the following description which, together with theaccompanying drawings, discloses two examples of the devices embodyingthe concepts of this invention.

Another feature of one construction involves Fig. 1 shows the focusingand centering device of this invention mounted on the neck of a cathoderay oscillograph tube;

Fig. 2 is a side elevation view and centering device according to thisinvention with portions broken away to show the relation of the internalelements of the device;

' Fig. 3 is a plan view taken on the line 2-3 of Fig. 2 to showthe'mounting of the shunt and outer sleeve actuatedby the gear; andrack;

Fig. 4 is a plan view taken on theline [-4 of Fig. 2 to show one of thecam operated plates of the focusing 1 flow ofjthe beam along the axis ofthe device or tube to counteract the effect of external ma8-' neticforces and to realign the beam or center I it, along the axis of thetube to compensate for controlling the shifting of the centering ringshown in cross-section; .Fig. 5 is another plan view ring by the otherslidable plate;

Fig. 6 is a partial plan view in cross-section taken on the line 6-6 ofFig. 2 showing the relation of the core, shunt and sleeve and the guidesfor the pins projecting from the shunt;

Fig. 6a is a cross-sectional view on the line 6H1: of Fig. 6 toillustrate the core magnetclamped between the end pole-pieces; r b

Fig. 7 is a plan View showing the relation of the superimposed slidingplates as viewed from the rear of the device and is taken on the linetaken on the line' 5-5 of Fig. 2 for the movement of the centerin 1-1 ofFig. 2, the centering ring being removed r and the plates shown indotted line;

Fig. 8- illustrates in a side elevation view another form 1 of theinvention with a portion in crosssectionto show the internal assembly;

Figs. 9 and9a are two rear plan views of the device of Fig. 8 showingthe'various positions of the link controls for shifting the centeringelement of the device;

manufacturing inaccuracies produced in the a mounting of the electrongun in the deviceor to P sition the spot on the-screen'in centralrelation to a scale superimposed on the screen.

The constructional details of the compact assembly of one embodiment ofthe adjustable magnet structure or unit, according to thisinvention,

are shown in Figs. 2 to "l, inc lusiva'Fig. 2 showing the combined unitand the other figures showing.

specific details of the unit. The structure has a central annular coreor permanent magnet 25 .of magnetic material having high flux density,

such as iron-nickel-aluminum alloys, of small mass andlargemagnetizingforces. A specific desirable material for the purposes ofthis in-.

vention is .Alni'co No. 2 or 5".having the general composition ofl'l percent nickel, 11 per cent aluminum, 12 per cent cobalt,- 6 percent copperand the remainder iron. Such an alloy. when suitably subjected to'heattreatment, is characterized byhigh .magnetislnretentivityregardless of'wide' temperature condition's'of operation andsusceptibility to impact forces which usually cause materialdeterioration in the magnetic properties of other types of permanentmagnets Y come 25 which forms the main component of the adjustablemagnetic focus'ingand centering structure or unit is coaxially mountedbetween top and bottom ring pole-pieces 26 and 21,:

respectively, of magnetic material,- such as steel.

The ring pole-piece 26 is provided with a'central opening 28 having adiameter substantially equiv- Fig. 10 is a front plan view of thedeviceof Fig. 8 showing the location of the group controls at the lowerend thereof;

Fig. 11 shows in cross-section a view along the line I l-l l of Fig. 8to illustrate the drive for the ,Fig. 14 is a cross-sectional viewin-elevation of the plates and centering element as shown in Fig. 13;and I Fig. 15 shows in perspective the relation'of the rotating sleeve,shunt and top pole-piece of the device, shown in Fig. 8.

Referring to Fig. 1 of the drawings, the compact adjustable magneticfocusing and centering structure or unit 20 of this invention is shownmounted on the cylindrical neck portion 2| of a cathode ray oscillographdevice or tube provided with a terminal base 22 at one end and a conicalportion 23 at the other end which terminates in a dome-shaped screen 24of large diameter. The screen is provided with an internal coatin ofmaterial which becomes fluorescent when an electron beam is projectedfrom an electron gun or source, not shown, but situated in the lower endof the neck portion 2 I. The magnetic structure 20 of this invention isemployed to influence the beam of electrons projected toward thescreen Iby a magnetic focusing field which'increases thedefinition of thefluorescent spot appearing on the screen and to adiustably correct thedirective ,alent to the diameter of the neckportionll of.

the cathode ray device and a cylindrical projecting portion 29 whichextends; exterior to the upper end of the core magnet 25. ThebottomDolepiece 21 has a larger diameter central opening coaxial with the coreand top pole-piece and is largerin diameter than the top pole-piece;This poie-pieceis provided with a rearwardly extending portion 30 aroundthe inner rim and the outer periphery is provided with a recess or shelfportion ii on the surface opposite the extending portion 30. Arectangular bearing plate 32, of

non-magnetic material, such as brass or aluminum, having a circularopening is fitted over the extension 30 of the pole-piece 2-! to reston. the flat surface of the pole-piece. The bearing plate 32 and bottompole-piece 21 are secured together by bolts 33 distributed in pairs inuniformly spaced relation and extending vertically around the exteriorof the core 25 to the extension 29 of the top pole-piece 26 and arethreaded therein,

- as shown in Fig. 6a, to rigidly clampthe polepieces together and thecore coaxially therebetween. The bolts are surrounded by non-magneticspacer sleeves 34, preferably of aluminum,

between the opposed. surfaces of the top and bottom pole-pieces. Amounting plate 35 having a central opening coincident with the opening28 of the top pole-piece and an angular extension at-the lower end issecured on the front of the top pole -pieceto rigidly support thpermanent magnet structure on a suitable base.

A cylindrical metallic shunt member 35, preferably of steel,surroundsthe'extensi'on 29 of the top pole-piece and; in .slidableengagement therewith. The shunt eir'ten'ds beyond the lower end of theextension "Land the projecting por..'

tion is provided with a plurality of radial pins '11 which extendthrough the shunt in equallythey. bmlect. from theinner and.onterzsurfaoesfpins arepositioned between the pairs of sleeves .34' onthe: bolts and are slidablymovable in reclprocal relation. in theguidesformedby: the sleeves;

thereby preventing rotational movement; of the; shunt with respect :tothe magnet core. The

shunt, however, is reciprocally movable to vary the flux field in thegap between the pole-pieces;

the position of .the shunt, as shown in Fig. 2, .10.

for the tube, for example, from 3,000 to 7,000

volts. Furthermore, the adjustment of the shunt is accurately controlledwith a minimum of frictional loss in the manipulation of the shunt withrespect to the pole-pieces and core magnet of the structure.

The shunt is actuated by a rotatable metallic sleeve 38 of non-magneticmaterial, such as brass, which surrounds the shunt member. This sleeveis of such diameter that it is seated on the shelf 3| on the peripheryof the bottom polepiece 21 and the opposite edge is in contact with awave-form phosphor bronze resilient ring 35, surrounding the toppole-piece 26 and lying against th mounting plate 35, to prevent endplayin the sleeve and to compensate for expansion and contraction in thestructure or unit. The sleeve 38 is provided with a plurality ofangularly directed slots 40 extending upwardly from one edge and theseslots form guideways for the travel of the pins 31 on the shunt member.The sleeve is also provided with a gear rack 4| which is soldered to theexterior surface of the sleeve above one of the slots 40. A spur gear 42carried by a rotatable shaft 43 engages the rack to impart movement tothe sleeve when the shaft is rotated. The shaft 43 extends between thebearing plate 32 and the mounting plate 35 and is locked in longitudinalposition by a stop collar 44 below the mounting plate. The extension ofthe shaft beyond the front of the mounting plate permits a suitablecontrol knob to be attached thereto or a flexible cable may be coupledto the shaft so that the sleeve may be rotated by remote control, forinstance, from a panel adjacent the screen 24 of the cathode ray device.

An auxiliary ring member 45, preferably of steel, is mounted in facingcontact with the annular extension 30 of the bottom pole-piece 21 incoaxial relation to the opening in the polepieces and magnet core 25.The ring 45 is slidably controlled to eccentrically olfset the axis ofthe ring with respect to the axis of the unit to counteract the mainflux field thereby shifting the beam of the cathode ray device tocompensate for the effect of the earth's magnetic field and also tocorrect axial symmetry of the beam with respect to the axis of thescreen 24, due to manufacturing inaccuracies in mounting the electrongun in the neck of the cathode ray tube.

The magnetic ring 45 is offset with respect to, the axis in onediametrical direction by a slidable plate 46 and in a transversedirection by a similar slidable plate 41, to shift the ring indirectional paths perpendicular to each other and thereby eliminatecurvilinear travel of the ring member 45 which would.- cause'thebeamtarotate the axis-oz: members tire-centering operation. The slidableplates are formed or non-magnetic material, suchas brass: 'or alue--mm.. and. provided with. an ovaf shaped largecentral opening? 48 whi'ch;encompasses the: centering ring 45, the small dimension of the openingin each plate beingthesametdlameter. as V the ring member 45 Sothat theplates have only. aJimited eo'ntact with the ringand the contacts-on oneplate being oriented 90v degrees. with respectto, the-contacts on. theother plate. It will be noted from an inspection of Figs. 4 and 5 thatthe contacting edges of the plates with the centering ring areperpendicular to the direction of travel of the slidable plates 46 and41 so that positive transverse movement of the ring is assured withoutloss of motion in the shifting operation of the ring. The free spacewithin the opening of each plate permits the ring to be shifted byeither plate depending on the direction intended to center the beam inthe cathode ray tube. The thickness of each of the slidable plates isone-half the thickness of the ring member 45 so that the surroundingmovable plates are flush with the ring.

The plate 46 slides across the rigidly mounted bearing plate 32 betweena, pair of edge guiding strips 49 and the slidable plate is providedwith an elongated recess 50 adjacent one edge in contact with a guidestrip to form a pocket for an arcuate wire spring 5|, to prevent bindingof the plate in the guideway of the bearing plate and to compensate forexpansion and contraction of the contacting parts of the unit. Theslidable plate 46 is also provided with a slot 52 of U-shaped contour inone corner thereof opposite the recess 5| and the slot is centrallyextended, as shown at 53, to form a relief opening to prevent binding inthe slot 52. The opposite corner of the plate 46 on the same edge as theslot is cut out, as shown at 54, to form a clearance slot. The slidableplate 41 engagesguide strip 55 on a back bearing plate 56, also ofnon-magnetic material, the strips 55 extending along opposite edges ofthe plate perpendicular to the strips 49 on the front bearing plate. Oneedge of the plate 41 is provided with a central elongated recess 51 toreceive an arcuate tension spring 58 and the lefthand corner of theplate is cut out, as shown at 59, to form a clearance slot. The slidableplate 41 is also provided with a corner slot 60 of U-shapedconfiguration with a relief opening 6| similar to the other slidableplate, the slot 60 being in the right-hand lower corner of the plate, asviewed in Fig. 5, but when the plates are assembled in facing relationon the bottom pole'piece, as shown in Fig. 7, the slot 60 is oppositelydisposed with respect to the slot 52 at the lower end of the unit and.extends in transverse direction thereto. The back bearing plate 56 issecured in facing relation to the front bearing plate 32 by screws 62with the guide strips thereon in perpendicular parallel relation withrespect to each other and the slidable plates held therebetween formovement in transverse relation.

A circular cam member or disc 63 is located in slot 52 in the slidableplate 46 and is connected eccentrically to a rotatable shaft 64 whichextends through the mounting plate 35 and front bearingplate 32, the camdisc being in frictional contact with the movable plate 46 toreciprocally slide the plate horizontally in the guideway of the bearingplate. Another cam disc 65 is located in the slot 60 and is connected toa parallel shaft 66 extending through the mounting plate 36, the

cam operating the sliding plate 41 reciprocallyin a vertical directionin the guideway in back bearing plate 56. The relief openings in the camslots eliminate binding of the cams in theslots and thereby permit freeoperation of the cams to slidably adjust the movable plates and thecentering ring therewith eccentrically with respect to the axis of theunit, whereby the beam in the cathode ray tube is accurately centered onthe screen 24. A resilient ring member 61 is secured between a metallicretainer ring 68 and the back bearing plate 56 by screws 69 prior to theattachment of the plate to the unit. The resilient ring, usually ofrubber or similar material, aids in centering the neck of the cathoderay tube in the magnet structure and compensates for irregularities inthe diameter thereof.

Another form of the invention is shown in the assembly of Figs. 8 to 12,inclusive, and certain details thereof as shown in Figs. 13 to 15,inclusive. The principal difference in this construction is the groupingof the controls for the movable elements of the unit at the bottomthereof and the coupling of the controls to the elements. As shown inFig. 8 the central permanent magnet core 25 is mounted coaxially betweena top ring pole-piece 26 and a bottom ring pole-piece 10 with a frontmounting plate 1| superimposed on the top pole-piece and the combinedelements securely clamped in coaxial relation by a plurality of bolts 12located in spaced relation between the periphery of the core 25 and theextension 29 of the top pole-piece. The bottom polepiece 10 is providedwith an annular recess 13 on the outer surface adjacent the inner edgeand is also provided with a plurality of diagonal slots 14, as shown inFig, 12, distributed in spaced relation around the periphery of thepole-piece. A back mounting plate 15 having the same configuration asthe front mounting plate II is secured in suitable spaced relationthereto adjacent the bottom pole-piece 10 by a plurality of bolts I6disposed exterior to the top pole-piece 26 and extending through theslots 14 of the bottom pole-piece to secure the mounting plate inuniform parallel relation, the bolts being provided with non-conductingspacer sleeves TI to insure uniform relation between the mountingplates. A similar pair of bolts and cooperating sleeves extend betweenthe mounting plates to space the extensions of the plates in uniformrelation.

A reciprocally movable shunt member 36 of magnetic material, such assteel, is slidably positioned around the extending portion 29 of the toppole-piece 26 and is provided with a plurality of pins 31 adjacent theexterior upper edge to extend radially into slots 40 of the rotatablesleeve 38 which is disposed between the front mounting plate H and thebottom pole-piece 10, the sleeve 38 being provided with a gear rack 4|in the same manner as described in connection with Fig. 2. An auxiliaryring member 18, of magnetic material, such as steel, is also slidablypositioned in the annular recess 13 of the bottom pole-piece 10 and isprovided with a plurality of outwardly projecting pins 19 disposed inrectangular relation adjacent the inner edge of the ring member.

The movable ring member 18 is controlled eccentrically with respect tothe axis of the magnet unit in a vertical direction by a slidablenonmagnetic plate 80 having a central rectangular cut-out portion 8|,opposed parallel edges of the plate in the opening perpendicular to thetravel of the slidable plate engaging the projecting pins '19 of theslidable ring 18, and the outer edges of the plate parallel to thedirection of travel of the plate being in contact with the guide sleeves11 extending across the gap between the back mounting plate 15 and thebottom pole-piece 10. A similar non-magnetic slidable plate 82 ismounted in transverse relationto slidable plate 80 and is provided witha central rectangular cut-out portion 63 having parallel edgesperpendicular to the direction of travel of the plate 62 in contact withthe projecting pins 19 of the ring member 18 and the outer edgesparallel to the direction of travel of the plate in contact with theguide'sleeves TI to reciprocally actuate the plate 82 in transverserelation to the vertical slidable plate 80 to eccentrically displace theauxiliary magnetic ring member 18 with respect to the axis of the unit.Both plates are provided with relief slots 84 at both ends adjacent oneedge to compensate for expansion and contraction of the plates and toprevent binding between the common guide sleeves for the plates. Theslidable plate 86 is provided with an outwardly projecting cylindricalmetallic block rigidly secured to the lower end of the plate and theslidable plate 82 is provided with a similar cylindrical block 86, theblocks extending through circular openings 81 and 88, respectively, inthe back mounting plate 15, The back mounting plate 15 is provided witha recess 89 on the inner surface adjacent the inner edge to provide afree path for the movement of the projecting pins 19 on the centeringring 18.

The reciprocally movable shunt member 36 and the transversely movablemagnetic ring 18 are controlled remotely by a, plurality of flexiblecables 90, BI and 92, shown in Fig. 10, extending into the lower portionof the front mounting plate II for actuating the controls coupled to themovable elements of the unit. The cable 96 is connected to a rotatableshaft 93 extending between the mounting plates H and 15 and a spur gear94 affixed to the shaft in line with the gear rack 4| on the rotatablesleeve 38 is coupled to the rack through an intermediate larger gear 95attached to a shaft 96 extending between the mounting plates torotatably actuate the sleeve 36 through a definite arc whereby theangularly directed slots 40 in the sleeve induce the pins 31 on theshunt member 36 to ride in the slots and thereby displace the shuntmember 36 reciprocally with respect to the pole-pieces to vary thestrength of the flux field in the gap of the magnet structure. The shuntmember 36 is prevented from rotational movement due to the fact that thepins 31 are. in contact with the guide sleeves 'Il disposed between theshunt member and the sleeve 38, as shown in Fig. 11, so that the flux ofthe magnet unit may be accurately varied to focus the electron beam withhigh definition regardless of the range of voltages applied to thefocusing electrodes of the cathode my tube.

The control cable 9| extends into a shaft 9'! in parallelrelation to thecenter shaft 93 between the end mounting plates and is rigidly afilxedto tion engages the shoulder screw in the cam disc 98 and is coupled atthe other endv to the cylindrical block 36 by a similar shoulder screwcentrally attached to the block which projects from the left-hand sideof the slidingplate 92, as shown in Fig. 12,. The link member 99 iscentrally pivoted on the back mounting plate 10 by a shoulder screw I00.As shown in Fig. 9, the movable centering ring 10 is coaxially mountedin relation to the central openingin the rear mounting plate 15 with thelink member 99 in normal position for obtaining such concentricity.However, when the cam disc 98 is rotated through the flexible cablecoupling, as shown in Fig. 9a, the pivoted link member 99 converts therotating movement of the cam disc to a shifting movement imparted to thesliding plate 02 to oifset the axis of the ring member 18 with respectto the axis of the opening in the magnet unit. The control cable 92 iscoupled to a shaft IOI extending between the mounting plates Parallel tothe shafts 93 and 91 and is afllxed to a circular cam member or disc I02projecting from the outer surface of the back mounting plate 15. The camI02 is provided with an offset aperture to receive a shoulder screwcoupling a short link member I 03 thereto with the other end of the linkmember attached by a shoulder screw to the center of thecylindricalblock 85 on the vertical sliding plate 80. The cam disc I02controls the reciprocal movement of plate 0.0 through the linkage ofmember I03 whereby the rotation of the cam disc I02 is converted to ashifting movement of the plate through the link member I03 to adjust theposition of the slidable ring 18 in transverse relation to the shiftingmovement imparted to the ring by the sliding plate 82. This arrangementpermits the slidable ring 18 to be eccentrically displaced with respectto the axis of the magnet unit in reciprocal relation through twotransverse directions by the cooperative action of the cams, links andsliding plates to insure accurate control of the movable auxiliarymagnetic ring with respect to the axis of the unit. Furthermore, thecontrols both for the shunt and the slidable ring are grouped togetherso that flexible cables may be conveniently brought in a straight lineto a panel adjacent the screen of the cathode ray tube and therebyfacilitate reliable control of the movable elements of the magnetstructure.

While the invention has been disclosed in several specific embodimentsto achieve the reciprocal movement of the shunt member within the magnetstructure and the slidable centering ring on one end of the magnet unitin transverse directions and to prevent curvilinear travel of thecentering ring, it is, of course, understood that various modificationsmay be made in the detailed assembly of the structure without departingfrom the scope of the invention as defined in the appended claims.

What is claimed is:

1. In combination, a cathode ray tube includ-' ing a source of electronsfor projecting a beam along the length of the tube and a fluorescentscreen receptive to the beam to produce a spot thereon, and anadjustable permanent magnet structure surrounding said tube for focusingsaid beam on said screen comprising a cylindrical cor of magneticmaterial, a cylindrical magnetic shunt member surrounding said corehaving pins extending radially therefrom, a. metallic sleeve surroundingsaid shunt having guideways therein for said pins, and means forrotating said sleeve to reciprocally actuate said shunt with respect tosaid sleeve and core.

2. In combination, a cathode ray tube including a source for projectingan electron beam rounding said core having pins extending radiallytherefrom, a metallic sleeve surrounding said shunt having guidewaystherein for saidpins, means for rotating said sleeve to reciprocallyactuate said shunt with respect to said sleeve and core, and verticalguide means between said sleeve and core in contact with said pins.

3. In combination, a cathode ray tube including a source for projectinga beam of electrons and a fluorescent screen excited by the beam toproduce a spot thereon, and an adjustable permanent magnet structuresurrounding said-tube for focusing said beam in relation to said screencomprising a cylindrical core of magnetic material having high fluxdensity, a cylindrical magnetic shunt member surrounding said corehaving pins extending radially therefrom, top and bottom ringpole-pieces on the ends of said core, said top ring having a downwardlyprojecting extension, a non-magnetic sleeve surrounding said shuntmember having guideways therein for said pins, and means for rotatingsaid sleeve to reciprocally actuate said shunt with respect to saidpole-pieces, said shunt being in slidable engagement with saidextension.

4. In combination, a cathode ray tube including a source for projectinga beam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and an adjustable permanent magnet structuresurrounding said tube for focusing said beam in relation to said screencomprising a cylindrical core of magnetic material having high fluxdensity, top and bottom ring pole-pieces on the ends of said core, amagnetic shunt member surroundingsaid core havin s pins extendingtherefrom, a metallic sleeve surrounding said shunt member havingguideways therein for said pins, means for rotating said sleeve toreciprocally actuate said shunt member with respect to said pole-pieces,and parallel guide rods extending between said polepieces in the spacebetween said sleeve and shunt member.

5. Incombination, a cathode ray tube including a source for projecting abeam of electrons and a fluorescent screen excited by the beam toproduce a spot thereon, and an adjustable permanent magnet structuresurrounding said tube for focusing said beam in relation to said screencomprising a cylindrical core of magnetic material having high fluxdensity, a cylindrical magnetic shunt member surrounding said corehaving pins extending radially therefrom, to and bottom ring pole-pieceson the ends of said core, a metallic sleeve surrounding said shunthaving guideways therein for said pins, means for rotating said sleeveto reciprocally actuate said shunt member with respect to-saidpole-pieces, and pairs of rods clamping said core betweensaidpole-pieces, said rods forming vertical guides for the pins on saidshunt member.

6. In combination, a cathode ray tube! including a source forprojectingia beam of electrons and a fluorescent screen excited by saidbeam to produce a spot thereon, and an adjustable permanent magnetstructure surrounding said tube for focusing and positioning said beamin relation to said screen comprising an annular maznetic core havingpole-pieces at opposite ends and coaxial therewith, and a pair ofslidable plates engaging said centering ring and movable in transversedirections at right angles to each other to shift said ring withrespectto the axis of said magnet structure.

7. In combination, acathode ray tube including a source for projecting abeam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and an adjustable permanent magnet structuresurrounding said tube for focusing and positioning said beam in relationto said screen comprising a cylindrical core of magnetic material, anauxiliary magnetic ring member on one end thereof, a pair ofsuperimposed plates having openings therein mounted about said ringmember, and means for slidably shifting said plates in transversedirections to displace said ring member with respect to the axis of saidcore.

8. In combination, a cathode ray tube including a source 'for projectinga beam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and an adjustable permanent structuresurrounding said tube for focusing and positioning said beam in relationto said screen comprising a cylindrical core of magnetic material, anauxiliary ring member on one end thereof, a pair of superimposed plateshaving openings therein mounted about said ring member, and cam memberscoupled to said plates for reciprocally actuating said'plates intransverse directions perpendicular to the axis of said core toeccen-trically adjust said magnetic ring member with respect to the axisof said core.

9. In combination, a cathode ray tube including a source for projectinga beam of electrons and a, fluorescent screen'excited by said beam toproduce a spot thereon, and an adjustable permanentmagnet structuresurrounding said tube for focusing and positioning said beam in relationto said screen comprising a cylindrical core of magnetic material, acylindrical magnetic shunt member surrounding said core having pinsextending radially therefrom, a metallic sleeve surrounding said shuntmember having guideways therein for said pins, means for rotating saidsleeve to reciprocally actuate said shunt with respect to said sleeveand core, an auxiliary ring member on one end thereof, a pair ofsuperimposed plates having "openings therein mounted about said-ringmember, means for slidably shiftproduce a spot thereon, and anadjustable permanent magnet structure embracing said tube for focusingand positioning said beam in relation to said screen comprising acylindrical core of magnetic material, top and bottom ring pole-pieceson the ends of said core, an auxiliary ring member in contact with theface of said bottom polepiece, a pair of superimposed plates havingopenings therein mounted about said ring member, means for slidablyshifting said plates in transverse directions to displace said ringmember with respect to the axis of said bottompole-piece, and rigidlymounted guide means projecting from said bottom pole-piece engaging theedges of said plates.

12. In combination. a cathode ray tube including a source for projectinga, beam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and an adjustable permanent magnet structureembracing said tube for focusing and positioning said beam in relationto said screen comprising a cylindrical core of magnetic material, topand bottom pole-pieces on the ends of said core, an auxiliary ringmember in contact with said bottom pole-piece, a pair of slidabie platesin facing relation around the periphery of said ring member, bearingplates in contact with the outer surfaces of said slidable plates, eachof said bearing plates having parallel guide strips on the edgesthereof, the guide strips on one bearing plate being perpendicular tothe strips on the other bearing plate, and cam members extending throughone of said bearing plates and engaging said slidable plates.

ing said plates in transverse directions to displace and a fluorescentscreen excited by said beam for,

producing a spot thereon, and an adjustable permanent magnet structuresurrounding said tube for focusing and positioning said beam in relationto said screen comprising a cylindrical core of magnetic material, topand bottom ring polepieces on the" ends of said core, an auxiliary ringmember in contact with said bottom pole-piece,

.the axis of said core.

13. In combination, a cathode ray tube includ-. ing, a source forprojecting a beam of electrons and a fluorescent screen excited by saidbeam to produce a spot thereon, and an adjustable permanent magnetstructure having a cylindrical core of magnetic material embracing saidtube for influencing said beam in relation to said screen, an auxiliaryring on one end of said core, a pair of slidable plates in facingrelation around the periphery of said ring, bearing plates in contactwith the opposite surfaces of said slidable plates,

each of said bearing plates having parallel guide strips on the edgesthereof, the guide strips on one bearing plate being perpendicular tothe strips on the other bearing plate, tension means interposed betweenadjacent edges of said slidable plates and guide strips, and rotatablecam members engaging said slidable plates to shift said plates intransverse directions perpendicular to 14. In combination, acathode raytube including a sourcefor projecting a. beam of electrons and afluorescent screen excited by said beam to produce a spot thereon, andan adjustable permanent magnet structure including a cylindrical core ofmagnetic material embracing said tube for influencing said beam inrelation to said screen, an auxiliary ring member on one end of saidcore, a pair of slidable plates in facing relation around the peripheryof said ring member, bearing plates in contact with the oppositesurfaces'of said slidable plates, each of said bearing plates havingparallel guide strips on the edges thereof, the guide strips on onebearing plate being perpendicular .to the strips on the other bearingplate, said slidable plates having open elongated recesses on one edgethereof, arcuate springs located in said recesses and engaging the guidestrips adjacent thereto, and rotatable cam members engaging saidslidable plates for shifting said plates in transverse directionsperpendicular to the axis of said core.

15. In combination, a cathode ray tube including a source for projectinga, beam of electrons and a fluorescent screen excited by the beam toproduce a spot thereon, and an adjustable permanent magnet structureincluding a-cylindrical core of magnetic material embracing said tubefor influencing said beam in relation to said screen, an auxiliary ringmember on one end of said core, a pair of slidable plates in facingrelation around the periphery of said ring member, bearing plates incontact with the opposite surfaces of said slidable plates, each of saidbearing plates having parallel guide strips on the edges thereof, theguide strips on one bearing plate being perpendicular to the strips onthe other bearing plate, said slidable plate; having open elongatedrecesses on one edge thereof, arcuate springs located in said recessesand engaging the guide strips adjacent thereto, said slidable platesalso having a slot in one corner thereof opposite said recess, and cammembers located in said slots and frictionally engaging said plates forreciprocal movement thereof in transverse directions perpendicular tothe axis of said core.

16. In combination, a cathode ray tube including a source for projectinga beam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and an adjustable permanent magnet structureincluding a cylindrical core of magnetic material embracing said tubefor influencing said beam in relation to said screen, an auxiliary ringmember on one end of said core, a pair of slidable plates in facingrelation having oval-shaped openings therein disposed about theperiphery of said ring member, bearing plates in contact with theopposite surfaces of said slidable plates, and cam members extendingthrough one of said'bearing plates and engaging said slidable plates,the portions of said slidable plates having the least diameter acrosssaid openings engaging said auxiliary ring member for initial movementthereof eccentric to the axis of said structure.

17. In combination, a cathode ray tube including a source for projectinga beam of electrons and a fluorescent screenexcited by said beam toproduce a spot thereon, and an adjustable permanent magnet structureincluding a cylindrical core of magnetic material surrounding the neckof said tube to influence said beam in relation to said screen, anauxiliary ring member on one end of said core, a pair of superimposedplates having openings therein mounted about said ring member, means forslidably shifting said platesin transverse directions to displace saidring member with respect to the axis of said core, and a yieldablecushion ring on the rear of said magnet structure adapted to engage theneck of the oathode ray device thereby centering the structure thereonand compensating for inequalities in the diameter of said neck. Y

18. In combination, a cathode ray tube including a source for projectinga beam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and an adjustable permanent magnet structureembracing said tube for focusing said beam in relation to said screencomprising a cylindrical core of magnetic material, top and bottom ringpole-pieces on the ends thereof, upright members extending between saidpolepieces and clamping said core centrally therebetween, a cylindricalshunt surrounding said core having spaced pins projecting from theexterior surface, a rotatable metallic sleeve surroundin said shunthaving angular slots extending from one edge thereof, said pin beinglocated in said slots and being slidably in contact with said uprightmembers, a gear rack on said sleeve, 9, pair of end plates secured tosaid pole-pieces in spaced relation, a rotatable shaft extending throughsaid plates at one end, and a spur gear on said shaft coupled to saidrack and supported between said plates.

19. In combination, a cathode ray tube including a source for projectinga beam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and a magnetic focusing and centering device forinfluencing the electron beam 01' said cathode ray tube and surroundingthe neck thereof, comprising an annular permanent magnet core of highflux density, top and bottom ring pole-pieces coaxially mounted on theends of said core, a cylindrical magnetic shunt member surrounding saidtop pole-piece and core, said shunt having pins extending radiallytherefrom, a mounting plate onsaid top pole-piece having an openingcoaxial with said pole-pieces and core, a non-magnetic sleeve having aplurality of angularly directed slots extending from one edge forreceiving said pins, said sleeve being mounted between said mountingplate and bottom pole-piece, an annular resilient metallic ring incontact with said mounting plate and sleeve, a gear rack on said sleeve,a rotatable gear shaft extending through said mounting plate coupled tosaid rack, an auxiliary flat ring member mounted on the exterior of saidbottom pole-pie ce, a pair of slidable plates having large centralopenings adjacent said auxiliary ring member and supported by saidbottom pole-piece, said plates being reciprocally movable in transversedirections perpendicular to the axis of said bottom polepiece to shiftsaid auxiliary ring member eccentrically, cam members coupled to saidslidable plates, and rotatable shafts extending through said mountingplate and attached to said cam members.

20. In combination, a cathode ray tube including a source for projectinga beam of electrons and a fluorescent screen excited by said beam toproduce a spot thereon, and a magnetic focusing and centering device forinfluencing the electron beam of said cathode ray tube and surroundingthe neck thereof, comprising an annular permanent magnet core of highflux density, top and bottom ring pole-pieces coaxially mounted on theends of said core, a cylindrical magnetic shunt member surrounding saidtop pole-piece and core, said shunt having pins extending radiallytherefrom, a mounting plate on said top pole-piece having an openingcoaxial with said pole-pieces and core, a non-magnetic sleeve having aplurality of angularly directed slots extending from one edge forreceiving said pins, said sleeve being mounted between said mountingplate and said bottom pole-piece, longitudinally mounted guide rodsclamping said core between said pole-pieces and disposed between saidcore and sleeve, said pins being in slidable contact with said rods toprevent rotational movement of said shunt member, a gear rack on saidsleeve, a rotatable geared cam members.

pled to said rack, an auxiliary flat ring member mounted on the exterioror said bottom polepiece, a pair of plates having large central openingstherein adjacent said auxiliary ring member and supported by said bottompole-piece, metallic guide members in contact with said plates to directsaid plates slidabiy in transverse reciprocal directions, individual cammembers for each of said plates, and rotatable shafts extending 10through said mounting plate and attached to said PHILIP T. SPROUL 16ammmcns crmn The following references are of record in the tile of thispatent:

5 UNITED STATES PATENTS Number Name v Date 2,224,933 Schlesinger -4.Dec. 17, 1940 2,336,837 Bedford Dec. 14, 1943 2,219,193 M91181], 001;.22, 1940 FOREIGN PATENTS Number Country Date 523,439 British ..-Jan 3,1939 472,165

British Mar. 11, 1936

